The invention concerns a measuring and indicating device for the position of a movable component relative to a measuring reference, and, more particularly, a measuring and indicating device for the position of a movable component relative to a measuring reference for the position of a slot defining the outlet gap of a paper machine headbox, or for a pertaining slot adjustment spindle, with an electrical signal emitter and an indicating device. Such a measuring and indicating device is used, for example, in a paper machine headbox for measuring the position of a slat defining the paper stock outlet gap or the position of a pertaining slat adjustment spindle. As is known, the said slat extends along the outlet gap across the entire machine width and is locally deformable for purposes of local fine adjustment of the outlet gap clearance. Provided for that purpose are numerous slat adjustment spindles arranged distributed across the machine width, which can be actuated individually or in groups. The deformation of the slat (at a specific point) must take place at high precision in very small steps, which normally are smaller than 1/100 mm. With the same precision, the local position of the slat (i.e., its state of deformation) must during the operation continuously be measured and indicated by means of a measuring and indicating device, on each of the adjustment spindles.
From the Voith brochure "Headboxes" (No. p 2503) it is known that on each of the movable adjustment spindles there is an electrical signal emitter arranged (called "path pickup" there) which measures the position of the spindle relative to a measuring reference. The latter is there for instance a so-called upper lip beam. Additionally, a mechanical indicating device is connected with the spindle. The electrical signal emitter serves the remote indication of the spindle position, and thus of the local position of the said slat (defining the paper stock outlet gap) fashioned preferably as a ruler-shaped profile bar. If required, the electrical signal emitter may also serve the transmission of the measured values to a process control system. The additionally present mechanical indicating device serves the reading of the position directly on the machine.
The presence of two measuring devices on each adjustment spindle has the advantage that the electrically measured data can be checked at any time by the preferably mechanical indicating device, and that the headbox--also in the event of a failure of the electrical measurement--can continue to be operated with the aid of the mechanical indicating device.
Difficulties, however, poses the safe installation of the two measuring devices in a way such that the measured values show a maximally exact agreement. In this respect, an improvement is sought by the invention.